Food, Energy & Digestion

Nutrition

  • Nutritional Requirements
  • Energy for external activity:
    • Reproduction
    • Seeking resources
    • Avoiding predation
  • Body maintenance & growth:
    • Energy needs vary at different life stages
  • Quality and Quantity of Food
  • Impacts consumption rates and amounts
  • Essential nutrients:
    • Proteins/amino acids
    • Vitamins and minerals
  • Availability of food affects survival and reproduction

What is Food?

  • Definition:
  • Energy expended should match energy intake from food
  • Forms of Food:
  • Proteins (amino acids)
  • Simple sugars (carbohydrates)
  • Fatty acids (lipids)
  • Vitamins and minerals
  • Energy Imbalance:
  • Excess energy leads to storage or metabolic disorders.
  • Insufficient energy affects health and reproductive success.

Feeding - How is Food Obtained?

  • Foraging:
  • Active search and acquisition of food.
  • Identification and consumption of food by vertebrates.
  • Adaptations:
  • Specialized behaviors like tool use in primates to access food.

Food Requirements

  • Dependent Factors:
  • Method of food acquisition
  • Quality and quantity of food resources
  • Energetic needs for both predator and prey
  • Baleen Feeding System:
  • Suspension feeding used by the largest mammals and certain fish.
  • Low energy intake system, so it's limited to specific scenarios.

Digestion - What Happens After Consumption?

  • Digestion Definition:
  • Breakdown of food molecules via enzymes or microbes into absorbable molecules
  • Methods of Breakdown:
  • Extracellular digestion using specialized organs (e.g., pancreas, liver).
  • Hydrolysis (addition of water) for molecular breakdown.
  • Digestive Enzymes:
  • Specific to foods; dependent on pH and temperature for activation.

Protein Digestion

  • Source:
  • Amino acids derived from protein intake.
  • Key Enzymes:
  • Pepsin (stomach): hydrolyzes peptide bonds in proteins.
  • Trypsin (midgut): further breaks down protein molecules.

Lipid Digestion

  • Process:
  • Breakdown of lipids into small droplets (emulsification) in the midgut.
  • Requirements:
  • Bile salts from the liver for emulsification.
  • Lipases secreted by the pancreas for digestion.
  • Effects:
  • Results in free fatty acids capable of cellular absorption.

Carbohydrate Digestion

  • Goal:
  • To convert carbohydrates into absorbable monosaccharides.
  • Breakdown Process:
  • Disaccharides targeted by specific enzymes (e.g., lactose by lactase).
  • Polysaccharides require multiple enzymatic actions (e.g., amylase for starch).
  • Cellulose digestion requires microbial symbiosis (not produced by vertebrates).

Digestive Tract Structure

  • Components Include:
  • Esophagus, stomach, small intestine, large intestine, rectum.
  • Associated organs like the liver, pancreas, gallbladder.

Herbivore Digestion

  • Types:
  • Intestinal Fermenters:
    • Rely on hindgut fermentation in large intestines and ceca.
    • Nutrients and some microbes may be lost during excretion.
  • Ruminants:
    • Multi-chambered stomachs allow for foregut fermentation and remastication.
    • Adaptations for low-quality food (e.g., zebras, cows).

Coprophagy

  • Definition:
  • Eating excrement to recover lost beneficial microbes post-defecation.

Carnivore Digestion

  • Characteristics:
  • Short digestive tract due to high nutrient density of meat.
  • Large acid production (60-70% of digestive tract in stomach).

Omnivore Digestion

  • Flexibility:
  • Diverse digestive systems allowing for a wide range of food resource utilization.

Absorption

  • Process:
  • Monosaccharides and free amino acids absorbed across membranes.
  • Small Intestine Features:
  • Length enhances absorptive surface area through folds, villi, and microvilli.
  • Optimized for effective nutrient transfer into blood and lymphatic systems.